1. Field of the Invention
This invention relates to a ball bearing of the type in which a retainer is guided by balls and in which the amount of radial movement during rotation is controlled, and to the retainer of such a bearing.
2. Related Background Art
An example of the conventional ball guide type retainer is shown in FIGS. 6 and 7 of the accompanying drawings. The peripheral wall of a retainer body 1a is provided with a plurality of pocket holes 3a having a diameter slightly greater than the diameter of balls 2a, each pocket having a peripheral wall 21a along (parallel to) the radial center line. The inner peripheral edge portion (or sometimes the outer peripheral edge portion) of each of the pocket holes is provided with restraining portions 4a for contacting the balls 2a during the rotation of the bearing to control the amount of radial movement of the retainer itself and to permit the retainer to rotate without contacting an inner race (or an outer race).
In the above-described conventional retainer, however, the restraining portions 4a are formed continuously along the entire periphery of each pocket hole 3a and therefore have points of contact with the balls 2a around the entire pocket hole periphery. This has led to problems such as heat generation and abrasion resulting from friction. Also, because it is difficult to precisely work the shape of the restraining portions, contact of the restraining portions 4a with the balls 2a may be non-uniform and unstable due to slight errors of dimensions and shape. These factors lead to collision noise between the retainer and the balls (so-called retainer noise) and/or heat generation.